Core assembly for winding sheet and winding method

ABSTRACT

A core assembly for a continuous sheet includes a core of a cylindrical form. A side channel is formed in the core to extend fully in an axial direction thereof. A shaft hub is disposed through the core movably in the axial direction. A changing unit or adjuster displaces the core in response to moving of the shaft hub between first and second positions, and enlarges an outer diameter of the core when the shaft hub is in the second position than when the shaft hub is in the first position. Preferably, the changing unit includes a cam roller, disposed on the shaft hub, for projecting in a radial direction. A cam ramp surface is formed with an inner surface of the core, has a height increasing toward the second position, is pressed by the cam roller.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a core assembly for winding a sheet and a winding method. More particularly, the present invention relates to a core assembly for winding a sheet to form a sheet roll without an internal support core in an efficient manner, and a winding method.

2. Description Related to the Prior Art

A continuous sheet or continuous film is a material of plastic film, paper or the like and is manufactured continuously. A sheet roll or film roll of the continuous sheet is provided in a form wound about an internal support core. As the sheet roll is shipped commercially in a form wound about the internal support core, the internal support core will be a waste produced to discard after use of the sheet roll.

Various methods of producing the sheet roll without the internal support core has been suggested. JP-A 6-127758 discloses the use of a core assembly or spool assembly in which air is blown or discharged to enlarge or reduce an outer diameter of the core assembly. Also, JP-A 2004-231399 discloses the core assembly in which a side channel is formed in the full length of its sleeve form. A first edge portion of the side channel is directed to lie under its second edge portion to reduce the outer diameter of the core assembly. In any of those methods, the continuous sheet is wound on the core assembly before reducing the outer diameter of the core assembly. The core assembly is removed from the sheet roll after the reduction of the outer diameter.

However, the method of JP-A 6-127758 has a problem in that a specific pump is required for blow and discharge of air, and will raise the structural cost. Furthermore, adjustment of the outer diameter of the core assembly is difficult because of easy compression of air. Differences between products as specificity will be considerably large in an inner diameter of the sheet roll determined by the outer diameter of the core assembly.

In JP-A 2004-231399, the outer diameter of the core assembly is not fixed. There is a drawback of failure in keeping high precision of an inner diameter of the sheet roll due to a change in the outer diameter of the core assembly in the course of winding the continuous sheet. This problem is typically serious in a surface winding method in which torque is applied to a peripheral surface of the core assembly for rotating the same.

SUMMARY OF THE INVENTION

In view of the foregoing problems, an object of the present invention is to provide a core assembly for winding a sheet to form a sheet roll without an internal support core in an efficient manner, and a winding method.

In order to achieve the above and other objects and advantages of this invention, a core assembly for winding a continuous sheet to form a sheet roll includes a core of a sleeve shape for winding the sheet thereabout. A side channel is formed in the core fully in an axial direction, for enabling an outer diameter of the core to change. A changing unit is disposed through the core movably in the axial direction, shifted to a first position before forming the sheet roll, and shifted to a second position before removing the core from the sheet roll, for pressing an inner surface of the core radially to enlarge the outer diameter when in the first position, and for releasing the inner surface from pressure to reduce the outer diameter when in the second position.

The changing unit includes plural cam rollers rotatable in contact with the inner surface. Furthermore, plural cam ramp surfaces are formed with the inner surface, pressed by the cam rollers in association therewith when the changing unit is in the first position.

The changing unit includes a shaft hub. Plural roller holders are arranged on the shaft hub, secured to first and second axial positions thereon, for projecting radially in each of the first and second axial positions, and for supporting the cam rollers rotatably at holder ends thereof.

Furthermore, plural receiving grooves are formed in the inner surface to extend in the axial direction, for receiving and guiding respectively the cam rollers.

Furthermore, the adjuster includes a cam projection for projecting from the shaft hub in a radial direction. A cam ramp surface is formed with an inner surface of the core, has a height increasing toward the second position, is pressed by the cam projection when the shaft hub moves toward the second position.

The cam projection includes a cam roller, caused by the cam ramp surface to rotate, for pressing the cam ramp surface while the shaft hub moves between the first and second positions.

The cam projection is constituted by plural cam projections of at least first and second groups, the second group is offset from the first group in the axial direction, and each of the first and second groups includes a predetermined number of cam projections arranged radially about an axis of the shaft hub.

Furthermore, a regulating device positions the shaft hub in the second position in the axial direction, to maintain a large diameter for the outer diameter.

The regulating device further positions the shaft hub in the first position in the axial direction, to maintain a small diameter for the outer diameter.

The regulating device includes a retaining hole formed in the inner surface of the core. A pin portion is formed to project from the shaft hub, for engagement with the retaining hole.

Furthermore, a regulating groove is formed in the inner surface of the core, for receiving and regulating the pin portion in the axial direction. The retaining hole is positioned at each of two ends of the regulating groove with respect to the axial direction, has a greater depth than the regulating groove, for retaining the pin portion.

The pin portion is constituted by a ball plunger.

Furthermore, a moving device is disposed on the shaft hub, for moving the pin portion in the radial direction between a retained position of entry in the retaining hole and a released position of release from the retaining hole.

The shaft hub includes an end opening formed in an end disposed close to the second position. A pull rod is secured through the end opening, and slidable in a push direction defined toward the first position and a pull direction defined toward the second position. The moving device is secured between the pull rod and the pin portion, moves the pin portion from the released position to the retained position when the pull rod is moved in the pull direction, and moves the pin portion from the retained position to the released position when the pull rod is moved in the push direction.

The moving device includes a link arm, having a first end secured to the pull rod in a rotatable manner, and a second end secured to the pin portion in a rotatable manner. A bias portion biases the pin portion toward the retained position.

Also, a winding method of winding a continuous sheet about a core assembly is provided. The core assembly includes a core of a sleeve shape, a side channel formed in the core fully in an axial direction, and a changing unit disposed through the core movably in the axial direction. In the winding method, the changing unit is shifted to a first position by moving through the core, for the changing unit in the first position to press an inner surface of the core radially to enlarge an outer diameter thereof. The core assembly is rotated to wind the sheet thereabout. After winding the sheet, the changing unit is shifted to a second position to release the inner surface from pressure to reduce the outer diameter. The core assembly is removed from a sheet roll of the sheet.

In one preferred embodiment, a method of forming a sheet roll includes a step of winding a continuous sheet about a core assembly, wherein the core assembly includes a core of a cylindrical form, a side channel formed in the core to extend fully in an axial direction thereof, an shaft hub disposed through the core movably in the axial direction, and an adjuster for displacing the core in response to moving of the shaft hub between first and second positions, and for enlarging an outer diameter of the core when the shaft hub is in the second position than when the shaft hub is in the first position. In the winding step, a large diameter is maintained for the outer diameter of the core assembly. The outer diameter is reduced after winding of the continuous sheet about the core assembly. The core assembly is removed from the continuous sheet being wound.

Accordingly, the core assembly can be used for forming a sheet roll without an internal support core in an efficient manner, because the outer diameter of the core can be adjusted stepwise for sheet winding.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will become more apparent from the following detailed description when read in connection with the accompanying drawings, in which:

FIG. 1 is a side elevation illustrating a film winding system;

FIG. 2 is a perspective view illustrating the film winding system;

FIG. 3 is an exploded perspective view illustrating a core assembly;

FIG. 4A is a front elevation illustrating a core;

FIG. 4B is a rear elevation illustrating the core;

FIG. 4C is a front elevation illustrating a changing unit;

FIG. 5A is an explanatory view illustrating the core assembly;

FIG. 5B is an explanatory view illustrating the same FIG. 5A but after enlarging the outer diameter;

FIG. 6A is an explanatory view in a section illustrating positioning of the changing unit relative to the core;

FIG. 6B is an explanatory view in a section illustrating the same as FIG. 6A but in a state of enlarging the outer diameter;

FIG. 7A-7H are explanatory views illustrating various steps in a sequence of winding a continuous sheet;

FIG. 8A is a front elevation illustrating a sheet roll wound about the core assembly;

FIG. 8B is a front elevation illustrating the same as FIG. 8A but after reducing the outer diameter;

FIG. 9A is an explanatory view illustrating another preferred core assembly;

FIG. 9B is an explanatory view illustrating the same as FIG. 9A but after enlarging the outer diameter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) OF THE PRESENT INVENTION

In FIGS. 1 and 2, a film winding system 11 or a film winding line is connected with a film production apparatus 12. Film web 13 is produced by the film production apparatus 12 continuously. A plurality of continuous sheets 13 a or continuous film of a strip shape are formed by slitting the film web 13. In the film winding system 11, a core assembly 41 or spool assembly or a winder winds the continuous sheet 13 a to obtain a sheet roll 71 or film roll. See FIG. 8.

The film winding system 11 includes a slitting roller 14, a blade receiving roller 15, guide rollers 16, 17, 18, 19, 20, 21, 22 and 23, surface rollers 24 and 25, a rider roller 26, a cutter 27, a CPU 28, motors 29 and 30, a lifting mechanism 31 and a cutter driving mechanism 32. In FIG. 2, elements are clarified in a simplified manner, so the rider roller 26, the cutter 27, the CPU 28, the motors 29 and 30, the lifting mechanism 31 and the cutter driving mechanism 32 are not illustrated.

A plurality of blades 14 a are included in the slitting roller 14, and arranged at a regular interval. Each of the blades 14 a has a shape of two frustums of a cone which are combined together by positioning their large circular surfaces on one another. The film web 13 moves on a path defined between the slitting roller 14 and the blade receiving roller 15 as pairs of upper and lower sides. An annular groove (not shown) is formed in the blade receiving roller 15 for partial entry of the blades 14 a of the slitting roller 14. The blades 14 a of the slitting roller 14 slit the film web 13 by shearing in passage between the slitting roller 14 and the blade receiving roller 15, to form a plurality of continuous sheets 13 a (five in the drawing).

The guide rollers 16-23 squeeze the film web 13 or the continuous sheet 13 a as plural pairs of rollers. A peripheral surface of the rider roller 26 contacts a peripheral surface of the guide roller 17. The guide roller 17 is rotated by rotation of the rider roller 26, to guide the continuous sheet 13 a to the rider roller 26.

The surface rollers 24 and 25 are arranged in parallel with one another with an interval. A plurality of the core assemblies 41 are disposed near to the surface rollers 24 and 25 for winding respectively the continuous sheet 13 a. Annular guide ridges 24 a are disposed on the peripheral surface of the surface roller 24 at a regular interval. The plural core assemblies 41 near to the surface rollers 24 and 25 are kept at a regular interval. The surface rollers 24 and 25 rotate by themselves to rotate the core assemblies 41. A rotational direction of the surface roller 25 is equal to that of the surface roller 24. Their forward rotational direction is clockwise in the drawing. Their backward rotational direction is counterclockwise.

The rider roller 26 is disposed higher than the surface rollers 24 and 25, and movable up and down in parallel with those. The rider roller 26, when shifted down, contacts a peripheral surface of the core assembly 41, to keep the core assembly 41 positioned in cooperation with the surface rollers 24 and 25. The rider roller 26 is rotated by rotation of the core assembly 41.

The rider roller 26 moved down contacts the guide roller 17, and guides the continuous sheet 13 a from the guide roller 17 toward the core assembly 41. The rider roller 26 winds the continuous sheet 13 a about the core assembly 41 in cooperation with the surface rollers 24 and 25, and forms the sheet roll 71 of FIG. 8. The rider roller 26 moves up in contact with an outer surface of the sheet roll 71 in response to the increase in the diameter of the sheet roll 71. Note that a surface winding method as a term used herein means a method in which the core assembly 41 is rotated by force applied to its peripheral surface to wind the continuous sheet 13 a.

The cutter 27 is disposed upstream from the core assembly 41 placed on the peripheral surface of the surface rollers 24 and 25. The cutter 27 cuts the continuous sheet 13 a to separate the sheet roll 71 about from an unwound portion of the continuous sheet 13 a. See FIG. 8.

The CPU 28 controls the entirety of the film winding system 11 for actuation of the motors 29 and 30, the lifting mechanism 31 and the cutter driving mechanism 32. The motors 29 and 30 rotate respectively the surface rollers 24 and 25. The lifting mechanism 31 moves the rider roller 26 up and down. The cutter driving mechanism 32 drives the cutter 27.

In FIGS. 3, 4A, 4B and 4C, the core assembly 41 includes a core 42 or outer sleeve and a changing unit 43 or inner shaft unit. An example of material from which the core 42 is formed is synthetic resin. The changing unit 43 of metal is disposed inside the core 42.

There is a side channel 44 or slit formed in the core 42 to extend in its longitudinal direction. The core 42, when pressed with internal pressure, expands with a larger outer diameter. The core 42, when application of the internal pressure is discontinued, comes to have an original diameter by its recovery force.

The changing unit 43 includes a shaft hub 45, cam rollers 46, 47, 48, 49, 50, 51, 52 and 53, ball plungers 54 and 55 as a regulating device, and a grip projection 56.

The shaft hub 45 is cylindrical. The cam rollers 46-49 and 50-53 are secured by roller holders 45 a to the peripheral surface of the shaft hub 45 and arranged at points of four even intervals at two ends with respect to its axial direction. The cam rollers 46-53 rotate and move on the inner surface of the core 42 in the axial direction.

The ball plungers 54 and 55 as retaining portions or pin portions are included in one pair, and protrude between the cam rollers 50 and 53 and between the cam rollers 51 and 52 near to one end of the shaft hub 45 as viewed in the axial direction. Balls 54 a and 55 a are rotatably disposed at ends of pin portions of the ball plungers 54 and 55. A compression coil spring (not shown) is contained in the inside of the respective pin portions and biases each of the balls 54 a and 55 a in a direction for protrusion. The balls 54 a and 55 a, when depressed, move to the inside of the pin portions against the bias of the coil spring, and when released from the depression, move back to the initial positions with the bias of the compression coil spring.

The grip projection 56 is disposed on one end surface of the shaft hub 45 to protrude in the axial direction. The grip projection 56 is manually pushed or pulled to move the changing unit 43 inside the core 42 axially.

Thick wall portions 57 and 58 of an annular shape are formed inside the core 42 and near to sleeve ends in the axial direction. Receiving grooves 59, 60, 61 and 62 are formed in the thick wall portions 57 and 58 in an equidistant manner in the peripheral direction. The receiving grooves 59-62 extend in the axial direction of the core 42 to define paths of the cam rollers 46-49 and 50-53.

Each of the receiving grooves 59-62 includes a large diameter portion (root), a small diameter portion (top) and a cam ramp surface 66. The large diameter portion has a small height, and a relatively large inner diameter of the core 42. The small diameter portion has a large height, and a relatively small inner diameter of the core 42. The cam ramp surface 66 extends between the large and small diameter portions. The cam rollers 46-53 are entered in the receiving grooves 59-62 rotatably and movably.

There are regulating grooves 63 and 64 with a click as regulating device. A movable range of the cam rollers 46-53 is limited by the ball plungers 54 and 55 and the regulating grooves 63 and 64. The cam rollers 46-53 rotate and move in the receiving grooves 59-62 between one end position where retaining holes 63 a and 64 a with a click are engaged with the balls 54 a and 55 a (See FIG. 6A) and another end position where retaining holes 63 b and 64 b with a click are engaged with the balls 54 a and 55 a (See FIG. 6B).

The regulating grooves 63 and 64 are formed in the thick wall portion 58 with inclinations, and disposed between the receiving grooves 59 and 62 and between the receiving grooves 60 and 61. The regulating grooves 63 and 64 extend in the axial direction of the core 42, and are paths of the balls 54 a and 55 a of the ball plungers 54 and 55. The retaining holes 63 a and 63 b are formed at ends of the regulating groove 63 of FIGS. 6A and 6B. The retaining holes 64 a and 64 b are formed at ends of the regulating groove 64.

In FIG. 5A, the cam rollers 46-53 are set on the large diameter portion of the receiving grooves 59-62, namely first position. An outer diameter of the core 42 is D1. When the cam rollers 46-53 are rotated and moved up in contact with the cam ramp surface 66 and enter the area of the small diameter portion, namely second position, then the small diameter portion is pressed by the cam rollers 46-53 as illustrated in FIG. 5B. The outer diameter of the core 42 becomes as large as D2 which is equal to D1+ΔD. When the cam rollers 46-53 are moved back and rotated in contact with the cam ramp surface 66 and shifted down to the large diameter portion, then the cam rollers 46-53 discontinue application of pressure as illustrated in FIG. 5A. The outer diameter of the core 42 is reduced to D1.

When the cam rollers 46-53 are positioned at the large diameter portion of the receiving grooves 59-62 in FIG. 5A, the balls 54 a and 55 a of the ball plungers 54 and 55 are entered in the retaining holes 63 a and 64 a of the regulating grooves 63 and 64. See FIG. 6A. This keeps the changing unit 43 positioned with the core 42. An outer diameter of the core 42 is kept at D1. See FIG. 5A.

When the cam rollers 46-53 are rotated and moved up to enter the area of the small diameter portion, the balls 54 a and 55 a of the ball plungers 54 and 55 are pressed by edges of the retaining holes 63 a and 64 a and set inside the ball plungers 54 and 55. The balls 54 a and 55 a pressed to the inside of the ball plungers 54 and 55 continue being pressed by the regulating grooves 63 and 64. The ball plungers 54 and 55 move forwards in the regulating grooves 63 and 64 while the balls 54 a and 55 a are kept depressed.

When the cam rollers 46-53 enter the area of the small diameter portion of the receiving grooves 59-62 in FIG. 5B, the balls 54 a and 55 a are released from pressure of the regulating grooves 63 and 64. In FIG. 6B, the balls 54 a and 55 a are entered in the retaining holes 63 b and 64 b of the regulating grooves 63 and 64. This determines the position of the changing unit 43 relative to the core 42, of which the outer diameter is kept at D2. See FIG. 5B.

When the cam rollers 46-53 are rotated and moved back toward the large diameter portion, the balls 54 a and 55 a of the ball plungers 54 and 55 are pressed by edges of the retaining holes 63 b and 64 b and depressed to the inside of the ball plungers 54 and 55. The balls 54 a and 55 a continue being pressed by the edge of the regulating grooves 63 and 64. The ball plungers 54 and 55 move forwards in the regulating grooves 63 and 64 while the balls 54 a and 55 a are depressed.

When the cam rollers 46-53 return to the large diameter portion of the receiving grooves 59-62 in FIG. 5A, the balls 54 a and 55 a are released from pressure of the regulating grooves 63 and 64. In FIG. 6A, the balls 54 a and 55 a are entered in the retaining holes 63 a and 64 a of the regulating grooves 63 and 64.

Thus, the ball plungers 54 and 55 and the regulating grooves 63 and 64 position the changing unit 43 so as to set the outer diameter of the core 42 equal to the predetermined size D2, and also position the changing unit 43 so as to set the outer diameter equal to the predetermined size D1 which is D2−ΔD smaller than D2, by way of a regulating device. Also, the retaining holes 63 a and 64 a are formed with the regulating grooves 63 and 64. The ball plungers 54 and 55 have the balls 54 a and 55 a for retention in the retaining holes 63 a and 64 a by way of retaining portions or pin portions.

A process of winding the continuous sheet 13 a in the film winding system 11 is described now by referring to FIGS. 7A-7H. At first, a plurality of the core assemblies 41 are expanded with an enlarged outer diameter D2, and are manually aligned and placed on the peripheral surface of the surface rollers 24 and 25. See FIG. 7A.

The lifting mechanism 31 moves down the rider roller 26 as illustrated in FIG. 7B. Then the peripheral surface of the rider roller 26 contacts that of the core assembly 41, which is squeezed between the rider roller 26 and the surface rollers 24 and 25.

In FIG. 7C, the motors 29 and 30 cause the surface rollers 24 and 25 to rotate in a forward direction. The core assembly 41, the rider roller 26 and the guide roller 17 are rotated by rotation of the surface rollers 24 and 25. The guide roller 17 rotates to guide the continuous sheet 13 a to the rider roller 26. Thus, the continuous sheet 13 a from the guide roller 17 is directed to the core assembly 41. As the core assembly 41 rotates, the continuous sheet 13 a guided from the rider roller 26 is wound to form the sheet roll 71. The motors 29 and 30 stop rotation of the surface rollers 24 and 25 upon forming of the sheet roll 71.

In FIG. 7D, the lifting mechanism 31 moves up the rider roller 26. In FIG. 7E, the cutter driving mechanism 32 drives the cutter 27. In FIG. 7F, the cutter 27 cuts the continuous sheet 13 a, and separates the sheet roll 71 about the core assembly 41 from the continuous sheet 13 a before being wound about the core assembly 41.

The sheet roll 71 separated from an unwound portion of the continuous sheet 13 a upstream from the core assembly 41 is manually removed from the surface rollers 24 and 25. See FIGS. 7G and 7H.

A sequence of removing the core assembly 41 from the sheet roll 71 is described now by referring to FIGS. 8A and 8B. An inner diameter of the sheet roll 71 about the core assembly 41 in the film winding system 11 is initially equal to the outer diameter of the core assembly 41. See FIG. 8A.

When the grip projection 56 is pressed in, the cam rollers 46-53 of FIG. 5B at the small diameter portion of the receiving grooves 59-62 move and rotate in contact with the cam ramp surface 66 to come to the large diameter portion of FIG. 5A. An outer diameter of the core assembly 41 decreases from D2 to D1 which is equal to D2−ΔD.

The outer diameter of the core assembly 41 becomes smaller than an inner diameter of the sheet roll 71 to dechuck the sheet roll 71. See FIG. 8B. Finally, the core assembly 41 is manually removed from the sheet roll 71.

The outer diameter of the core assembly 41 is reduced after its expansion for winding the continuous sheet 13 a. The sheet roll 71 is dechucked and removed from the core assembly 41 with the reduced diameter, and can be produced without an internal support core. As the core assembly 41 is expanded with inner pressure of the changing unit 43 or inner shaft unit within the core 42 or outer sleeve, the sheet roll 71 can be produced with high precision in its inner diameter owing to a small change in the outer diameter of the core assembly 41 to wind the continuous sheet 13 a.

Another preferred film winding system is described now. A core assembly 76 or spool assembly as a winder of FIGS. 9A and 9B is installed in place of the core assembly 41 of the above embodiment. Elements similar to those of the above embodiments are designated with identical reference numerals.

The core assembly 76 includes a core 77 and a changing unit 78. A side channel 77 a or slit extends in the core 77 in its longitudinal direction. The changing unit 78 includes a shaft hub 79, cam rollers 80, 81, 82, 83, 84 and 85, a regulating rod 86, a compression coil spring 87, a moving device 88, a guide projection 89 or anti roll bar, and a grip projection 90.

The shaft hub 79 has a rod shape with shaft ends 79 a and 79 b. The cam rollers 80-82 and 83-85 are secured to the peripheral surface of the shaft hub 79 and positioned at points with a pitch of one third of a rotation at the shaft ends 79 a and 79 b of the shaft hub 79.

The regulating rod 86 is inserted through the changing unit 78 in a radial direction, and is slidable back and forth. A stopper 86 a is formed with the regulating rod 86, and positioned near to its one end outside the changing unit 78, for retention of a spring end of the compression coil spring 87. The compression coil spring 87 is disposed about the regulating rod 86, and between the stopper 86 a and an outer surface of the shaft hub 79. The regulating rod 86 is biased by the compression coil spring 87 in a direction to shift the stopper 86 a away from the shaft hub 79, namely downwards in the drawing. A pin portion 86 b of the regulating rod 86 is pressed against the inner surface of the core 77, to compress the compression coil spring 87.

The moving device 88 includes a pull rod 91 and a link arm 92. The pull rod 91 extends through the shaft end 79 a of the shaft hub 79. The grip projection 90 is secured to a front end of the pull rod 91 protruding through the shaft end 79 a. The pull rod 91 is slidable in the axial direction of the shaft hub 79, and is connected with the regulating rod 86 by the link arm 92. When the pull rod 91 moves in a direction of entry of the grip projection 90, namely to the left in the drawing, the link arm 92 moves the regulating rod 86 in a direction of compressing the compression coil spring 87, namely to the upper side in the drawing.

The guide projection 89 protrudes from an outer surface of the shaft hub 79. A guide groove 93 or keyway is formed in the inner surface of the core 77 to extend in the axial direction. An end of the guide projection 89 is inserted in the guide groove 93 and is movable along the same. The insertion of the end of the guide projection 89 in the guide groove 93 prevents the changing unit 78 from rotating inside the core 77.

A receiving groove 94 is formed in an inner surface of the core 77 and extends in the axial direction as a path of moving the pin portion 86 b of the regulating rod 86. A retaining hole 94 a is formed in one end of the receiving groove 94, namely at the right end in the drawing, for engagement of the pin portion 86 b of the regulating rod 86.

A movable range of the cam rollers 80-85 is limited by the guide projection 89, the guide groove 93, the regulating rod 86 and the receiving groove 94. The cam rollers 80-85 are caused to move and rotate in receiving grooves between a first position (See FIG. 9A) at a large diameter portion and a second position (See FIG. 9B) at a small diameter portion.

When the cam rollers 80-85 enter the area of the small diameter portion of a cam ramp surface 96 of the receiving groove (See FIG. 9B), the pin portion 86 b of the regulating rod 86 becomes received in the retaining hole 94 a of the receiving groove 94. In short, the pin portion 86 b of the regulating rod 86 moves from a released position away from the retaining hole 94 a to a retained position of receiving in the receiving groove 94. The changing unit 78 is positioned exactly relative to the core 77 by receiving the pin portion 86 b of the regulating rod 86 in the retaining hole 94 a. In FIG. 9B, the outer diameter of the core 77 is kept at D2.

When the grip projection 90 is depressed from a state of keeping the core 77 with the outer diameter of D2 of FIG. 9B, the moving device 88 operates to move the pin portion 86 b of the regulating rod 86 from the retained position to the released position against the bias of the compression coil spring 87. The cam rollers 80-85 become rotatable and movable by shift of the pin portion 86 b of the regulating rod 86 in the released position.

Thus, the retaining hole 94 a and the pin portion 86 b of the regulating rod 86 are combined by way of a regulating device for positioning the changing unit 78 to expand the core 77 with the outer diameter D2.

In operation of removal of the core assembly 76 from a film roll, an operator manually depresses the grip projection 90 to enable the cam rollers 80-85 to rotate and move. Those move from the small diameter portion and pass the cam ramp surface 96 to the large diameter portion, from the state of FIG. 9B to the state of FIG. 9A. The core assembly 76 can be pulled away manually, as its outer diameter decreases from D2 to D1.

In the above embodiment, the material to be wound is the continuous film. However, winding on the core assembly may be used for winding paper or other material of a continuous sheet form or film form.

Although the winding method is the surface winding method in the above embodiments, a winding method of the invention can be any one of known methods. For example, it is possible to hold a core assembly between two plates at ends of the core, and to cause the plates to rotate together with the core assembly in contact with the core. Furthermore, it is possible in another winding method to chuck ends of the core in contact with their inner surface by use of a chuck device, and to rotate the chuck device together with the core assembly in the chucked state.

Also, the tasks performed manually in the above embodiment can be performed automatically by industrial robots or the like, including setting of the core assembly in the film winding system, removal of the sheet roll, depression of the grip projection, and removal of the core assembly from the sheet roll.

In the above embodiments, the changing unit is supported at three or four points by use of three of cam rollers arranged equidistantly. However, the number of points at which the changing unit is supported may be two or five or more, for the purpose of keeping a circular form of the profile of the core in a predetermined limit. It is possible in the core to form receiving grooves of a number equal to the number of the points of support.

In the above embodiments, the core has one side channel. However, the core may have other forms in which the outer diameter is enlarged by inner pressure and becomes reduced again upon discontinuation of the inner pressure. For example, the number of the side channels may be two or more in the core. To this end, the core is constituted by plural plate-shaped parts. A structure for connecting the parts may be added. Also, a structure for biasing one of the parts to decrease the outer diameter may be added.

Note that the continuous sheet can have suitable rigidity in view of forming a sheet roll without an internal support core. If the rigidity of the continuous sheet is relatively higher than a reference rigidity, the shape of a cavity created after removal of the core assembly will be maintained without collapsing. If the rigidity of the continuous sheet is lower than the reference rigidity, a cavity created after removal of the core assembly will have a reduced shape because of weakness of the innermost turns of the sheet roll.

The changing unit of the above embodiment includes cam rollers for engagement with the cam ramp surface. However, other cam elements may be used in combination with the cam ramp surface, including cam roller balls, cam projections with a lubricant layer, which satisfy suitable conditions of low friction, high resistance to polish, and property for transmitting force to the cam ramp surface.

Although the present invention has been fully described by way of the preferred embodiments thereof with reference to the accompanying drawings, various changes and modifications will be apparent to those having skill in this field. Therefore, unless otherwise these changes and modifications depart from the scope of the present invention, they should be construed as included therein. 

1. A core assembly for winding a continuous sheet to form a sheet roll, comprising: a core of a sleeve shape for winding said sheet thereabout; a side channel, formed in said core fully in an axial direction, for enabling an outer diameter of said core to change; a changing unit, disposed through said core movably in said axial direction, shifted to a first position before forming said sheet roll, and shifted to a second position before removing said core from said sheet roll, for pressing an inner surface of said core radially to enlarge said outer diameter when in said first position, and for releasing said inner surface from pressure to reduce said outer diameter when in said second position.
 2. A core assembly as defined in claim 1, wherein said changing unit includes plural cam rollers rotatable in contact with said inner surface; further comprising plural cam ramp surfaces, formed with said inner surface, pressed by said cam rollers in association therewith when said changing unit is in said first position.
 3. A core assembly as defined in claim 2, wherein said changing unit includes: a shaft hub; and plural roller holders, arranged on said shaft hub, secured to first and second axial positions thereon, for projecting radially in each of said first and second axial positions, and for supporting said cam rollers rotatably at holder ends thereof.
 4. A core assembly as defined in claim 3, further comprising plural receiving grooves, formed in said inner surface to extend in said axial direction, for receiving and guiding respectively said cam rollers.
 5. A core assembly as defined in claim 3, further comprising a regulating device for retaining said changing unit in said first position.
 6. A core assembly as defined in claim 5, wherein said regulating device further retains said changing unit in said second position.
 7. A core assembly as defined in claim 6, wherein said regulating device includes: a first retaining hole formed in said inner surface; a retaining portion, secured to said changing unit, for entry in said first retaining hole to retain said changing unit in said first position.
 8. A core assembly as defined in claim 7, wherein said regulating device further includes a second retaining hole, formed in said inner surface, for positioning said changing unit in said second position upon entry of said retaining portion.
 9. A core assembly as defined in claim 7, further comprising a regulating groove, formed in said inner surface, for receiving said retaining portion, said first retaining hole being formed with said regulating groove.
 10. A core assembly as defined in claim 9, wherein said retaining portion is constituted by a ball plunger for retention in a releasable manner.
 11. A core assembly as defined in claim 9, further comprising a moving device for moving said retaining portion between a retained position of entry in said first retaining hole and a released position of release from said first retaining hole.
 12. A core assembly as defined in claim 11, wherein said retaining portion includes a regulating rod biased toward said retained position; said moving device includes: a projection, disposed at an end of said shaft hub, pulled for moving said changing unit from said second position to said first position, and pushed for moving said changing unit from said first position to said second position; and a rod, disposed through said shaft hub in a slidable manner, having one end provided with said projection, for moving said regulating rod toward said released position when said projection is pushed.
 13. A core assembly as defined in claim 12, wherein said moving mechanism further includes a link arm for connecting said rod and said regulating rod.
 14. A winding method of winding a continuous sheet about a core assembly including a core of a sleeve shape, a side channel formed in said core fully in an axial direction, and a changing unit disposed through said core movably in said axial direction, said winding method comprising steps of: shifting said changing unit to a first position by moving through said core, for said changing unit in said first position to press an inner surface of said core radially to enlarge an outer diameter thereof; rotating said core assembly to wind said sheet thereabout; after winding said sheet, shifting said changing unit to a second position to release said inner surface from pressure to reduce said outer diameter; removing said core assembly from a sheet roll of said sheet.
 15. A winding method as defined in claim 14, wherein said core assembly is supported by a pair of surface rollers disposed in parallel with one another, and is rotated by rotation of said surface rollers in a common direction. 